This invention relates to an optical probe used in a near-field effect microscope for a purpose of observing topography or measuring photo-physical properties at a solid surface in ranges of nano-meter by optically illuminating or photo-exciting a surface to be measured, a method of manufacturing the optical probe, a scanning probe microscope using this optical probe.
Conventionally, there has been used a probe possessing a microscopic aperture as an optical probe for near-field effect microscopes. As this microscopic-aperture optical probe, a basic principle is disclosed in U.S. Pat. No. 4,604,520. The basic structure has a metal coating formed in a thickness of less than 200 nano-meter over a portion, excepting a tip portion, of a quartz rod with sharply edged tip to form an aperture smaller than the wavelength of light at the tip. An evanescent field can be formed at the microscopic aperture portion at the tip by introducing light through a light inlet port provided on the opposite side to the aperture of the probe. Besides this, as a method for forming such an optical probe having a microscopic aperture is disclosed in J. Vac. Sci. Technol. B3, 386 (1985), wherein a metal film is deposited on a glass surface having fine particles put thereon and thereafter the fine particles are removed to form a microscopic aperture. Also, there is disclosed a probe manufacturing method in U.S. Pat. No. 4,917,462 wherein a glass tube is extended by heat until it is fractured to coat a metal film over a lateral surface of the glass so that a tip hole of a thinned glass tube is made as a microscopic aperture. Moreover, U.S. Pat. No. 5,272,330 discloses a probe manufacturing method that an optical fiber is extended until it is thermally fractured to metal-coat a lateral surface, making a microscopic aperture at a tip portion of the thinned optical fiber.
In the meanwhile, there is a disclosure as a functional probe by Lewis et al. in Nature 354, 1991, p. 214 that light is introduced into a functional probe of a glass tube having a probe tip packed with a fluorescent substance to use fluorescent light as a microscopic light source. This method, however, involves problems that the microscopic light source wavelength is restricted in selection and the light source intensity gradually decreases due to putting off of the fluorescent light.
The problem in the above microscopic-aperture optical probe lies in that the intensity of the evanescent field at the microscopic aperture greatly decreases 1/10000 to 1/1000 with respect to the intensity of incoming light. This acts to prevent against observations of samples at high S/N or processing/writing at high speed scanning.